The present invention relates to a facsimile apparatus and, more particularly, to a control device for a facsimile apparatus and capable of executing automatic call termination by detecting a terminating signal.
A facsimile apparatus with an automatic call terminating function is capable of entering into a call termination mode on detecting a terminating signal of 1,300 Hz input from a public telephone network. For this purpose, a receiver included in the apparatus has a function of detecting and identifying a 1300 Hz frequency component. The prerequisite with this function is that when noise components around 1300 Hz are received together with the terminating signal, the noise components be excluded.
It has been customary with the above facsimile apparatus to monitor only the 1300 Hz component with a terminating signal detection circuit. If the 1300 Hz component has a level higher than a predetermined level, the detection circuit determines that it is a terminating signal. Japanese Patent Laid-Open Publication No. 63-62467, for example, discloses a device for distinguishing a facsimile protocol signal and a speech signal by determining whether the protocol signal is a continuous pattern or whether it is an discontinuous pattern. Also, Japanese Patent Laid-Open publication No. 2-11056 proposes a device for distinguishing a speech signal and a data signal by detecting the frequency component of a received signal and then subjecting it to computation.
However, the conventional scheme which monitors only the 1300 Hz component has a problem that even noise containing a 1300 Hz component is determined to be the terminating signal if such a component is higher in level than the predetermined level. The continuous/discontinuous pattern scheme is apt to result in a detection error when continuous noise is received. Further, the distinction between a speech signal and a data signal is not practicable without resorting to large scale equipment.